A rack bar and pinion assembly of the type with which the present invention is concerned (hereinafter referred to as "the type specified") includes a pinion rotatively mounted in a pinion housing; a rack bar linearly movable in a longitudinal direction through said pinion housing; and a rack on said rack bar operatively connected with the pinion so that rotation of the pinion effects movement of the rack bar through the pinion housing.
A rack bar assembly of the type specified has been proposed in U.S. Pat. No. 4,215,591 for use in a vehicle, and this includes a support assembly adapted to support the rack bar in the pinion housing with rollers spring biased into contact with the side of the rack bar remote from the pinion under all steering loads. The rollers bias the rack bar towards the pinion and, thereby, the rack teeth into engagement with the pinion, but are intended to allow for efficient and ease of steering under light loads. The support assembly also includes plain bearing surfaces defining a wedge at a fixed distance from the pinion which the rack bar is intended to only contact under high loads such as when the rack bar is under shock loading. Such an arrangement is proposed to alleviate "rack-rattle" but tends to have the disadvantage that, for example, where heavy manoeuvres are undertaken such as in parking, the steering effort will be considerably greater to the driver than when driving generally in the forward direction and undertaking gentle manoeuvres. This is largely due to the rack bar under heavy loads being urged into wedging engagement with bearing surfaces which are plain and a fixed distance from the pinion.
It is an object of the present invention to provide a rack bar and pinion assembly in which the steering effort at high loads is not unduly increased.